System, method and device for time slot status messaging among SONET nodes

ABSTRACT

Described are a system and method of transmitting a time slot status message between nodes in a SONET network. One or more time slots in a SONET link may be allocated to provision a SONET circuit. Upon provisioning or de-provisioning the SONET circuit, a time slot status message may be transmitted to one or more non-participating nodes in the SONET network to indicate a change in status of one or more time slots of the SONET link.

BACKGROUND

1. Field

The subject matter disclosed herein relates to communication systems. Inparticular, the subject matter disclosed herein relates to communicationbetween nodes in a communication system.

2. Information

Telecommunication data networks typically include a network backbonecomprising fiber optic communication links coupling geographicallydispersed nodes. Data is typically transmitted across such a networkbackbone according to the “Synchronous Optical NETwork” (SONET) protocolas indicated in a set of standards provided by the American NationalStandards Institute (ANSI T1.105.xx) or “Synchronous Digital Hierarchy”(SDH) protocol as indicated in a set of recommendations provided by theInternational Telecommunications Union (e.g., ITU-T G.707, G.708, G.709,G.783 and G.784). Under the SONET/SDH protocol, a transmitting node maytransmit data frames referred to as “SONET frames” to a destinationnode.

Nodes in a SONET network are typically arranged in a “ring” topologycoupled by SONET links to transmit SONET frames between adjacent nodesin the ring. A node in a SONET ring may transmit a SONET frame othernodes by transmitting the SONET frame to either of two adjacent nodes inthe SONET ring. Accordingly, SONET frames may be transmitted betweennodes in a SONET ring in either a clockwise or counter clockwisedirection in the ring.

Resources in a SONET network may be dynamically configured in responseto service demands. A SONET link between nodes in a SONET ring may beshared among multiple communication circuits. Protocols described in aUser Network Interface 1.0 Signaling Specification, Oct. 1, 2001,published by the Optical Internetworking Forum, may be used forcommunication between nodes in a SONET network to facilitate the dynamicallocation of resources.

BRIEF DESCRIPTION OF THE FIGURES

Non-limiting and non-exhaustive embodiments of the present inventionwill be described with reference to the following figures, wherein likereference numerals refer to like parts throughout the various figuresunless otherwise specified.

FIG. 1 shows a topology of a Synchronous Optical Network/SynchronousDigital Hierarchy (SONET/SDH) network according to an embodiment of thepresent invention.

FIG. 2 shows a topology of a SONET ring in a SONET network according toan embodiment of the SONET network topology shown in FIG. 1.

FIG. 3 shows a schematic diagram of a system to transmit SONET frames ina SONET/SDH links according to an embodiment of the system topologyshown in FIG. 2.

FIG. 4 shows a flow diagram illustrating a process executed at a node inresponse to provisioning a SONET circuit according to an embodiment ofthe system shown in FIG. 3.

FIG. 5 shows a flow diagram illustrating a process executed at a node inresponse to de-provisioning a SONET circuit according to an embodimentof the system shown in FIG. 3.

FIG. 6 shows a format for a packetized time slot status messageaccording to an embodiment of the processes shown in FIGS. 4 and 5.

FIG. 7 shows a flow diagram illustrating a process initiated uponreceipt of a time slot status message at a node according to anembodiment of the packetized time slot status message shown in FIG. 6.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in one or moreembodiments.

“Machine-readable” instructions as referred to herein relate toexpressions which may be understood by one or more machines forperforming one or more logical operations. For example, machine-readableinstructions may comprise instructions which are interpretable by aprocessor compiler for executing one or more operations on one or moredata objects. However, this is merely an example of machine-readableinstructions and embodiments of the present invention are not limited inthis respect.

“Storage medium” as referred to herein relates to media capable ofmaintaining expressions which are perceivable by one or more machines.For example, a storage medium may comprise one or more storage devicesfor storing machine-readable instructions or data. Such storage devicesmay comprise storage media such as, for example, optical, magnetic orsemiconductor storage media. However, this is merely an example of astorage medium and embodiments of the present invention are not limitedin this respect.

“Logic” as referred to herein relates to structure for performing one ormore logical operations. For example, logic may comprise circuitry whichprovides one or more output signals based upon one or more inputsignals. Such circuitry may comprise a finite state machine whichreceives a digital input and provides a digital output, or circuitrywhich provides one or more analog output signals in response to one ormore analog input signals. Such circuitry may be provided in anapplication specific integrated circuit (ASIC) or field programmablegate array (FPGA). Also, logic may comprise machine-readableinstructions stored in a memory in combination with processing circuitryto execute such machine-readable instructions. However, these are merelyexamples of structures which may provide logic and embodiments of thepresent invention are not limited in this respect.

“Synchronous Optical Network” (SONET) as referred to herein relates to adata transmission protocol according to a set of standards provided bythe American National Standards Institute (ANSI T1.105.xx). “SynchronousDigital Hierarchy” (SDH) as referred to herein relates to a datatransmission protocol according to a set of recommendations provided bythe International Telecommunications Union (e.g., ITU-T G.707, G.708,G.709, G.783 and G.784). “SONET/SDH” as referred to herein relates toaspects of either a SONET or SDH protocol, or both. Hereinafter, “SONET”and “SONET/SDH” may be applied interchangeably.

“Data frames” or “frames” as referred to herein relates to a segment ofdata which is formatted for transmission from a source to a destination.A data frame may comprise a header portion and a payload portion. A dataframe may be formatted as a “SONET frame” for transmission in a datalink according to a data transmission protocol such as SONET/SDH.However, these are merely examples of a data frame and embodiments ofthe present invention are not limited in these respects.

A “node” as referred to herein relates to a physical location in acommunication network. Nodes in a communication network may be coupledby one or more data links. A node may be associated with source ordestination for data frames. However, these are merely examples of anode and embodiments of the present invention are not limited in theserespects.

A “SONET link” as referred to herein relates to a data link to transmitSONET frames between nodes. For example, a SONET link may comprise anoptical transmission medium coupled between a SONET framer at atransmitting node and a SONET framer at a receiving node. A SONET linkmay also comprise two or more aggregated optical transmission mediawhere each medium is coupled between a SONET framer at a transmittingnode and a SONET framer at a receiving node. However, these are merelyexamples of a SONET link and embodiments of the present invention arenot limited in these respects.

A “SONET network” as referred to herein relates to a plurality of nodescoupled by one or more SONET links to transmit SONET frames among thenodes. A “SONET ring” relates to a topology of nodes in a SONET networkcoupled by SONET links where each node is coupled to two other nodes inthe topology. For example, a first node in a SONET ring may transmit aSONET frame to a second node in the SONET ring by transmitting the frameto either of two adjacent nodes in the topology. However, these aremerely examples of a SONET ring and embodiments of the present inventionare not limited in these respects.

The data transmission capacity of a data link may be partitioned into aplurality of “time slots” that may be allocated among processes orservices. For example, distinct portions of the payload in SONET framestransmitted in a SONET link may be associated with distinct time slotswhere each time slot is allocated to a distinct service or process.However, these are merely examples of how data transmission capacity ofa data link may be partitioned into time slots and embodiments of thepresent invention are not limited in these respects.

A “SONET circuit” as referred to herein relates to a service to transmitdata between nodes in a SONET network over shared transmission capacityin shared SONET links. For example, for each SONET link coupling nodesin a SONET circuit, a portion of data transmission capacity may beallocated to the SONET circuit. However, this is merely an example of aSONET circuit and embodiments of the present invention are not limitedin these respects. A SONET circuit may be “provisioned” by allocatingone or more time slots of each SONET link coupling the nodes in theSONET circuit. However, this is merely an example of how a SONET circuitmay be provisioned and embodiments of the present invention are notlimited in these respects.

A “time slot status message” as referred to herein relates to a messagetransmitted between nodes in a data network indicating a status of atleast one time slot of a data link between nodes in a network. In aSONET network, for example, a time slot status message may indicate astatus of a time slot as either free or allocated to a SONET circuit.However, this is merely an example of a time slot status message andembodiments of the present invention are not limited this respects.

Briefly, an embodiment of the present invention relates to a system andmethod of transmitting a time slot status message between nodes in aSONET network. One or more time slots in a SONET link may be allocatedto provision a SONET circuit. Upon provisioning or de-provisioning theSONET circuit, a time slot status message may be transmitted to one ormore non-participating nodes in the SONET network to indicate a changein status of one or more time slots of the SONET link. However, this ismerely an example embodiment and other embodiments of the presentinvention are not limited in these respects.

FIG. 1 shows a topology of a SONET network according to an embodiment ofthe present invention. A plurality of nodes 12 are coupled in a SONETring topology by SONET links 18 where each SONET link 18 comprises acapacity to transmit data between nodes 12 in at least one direction(e.g., either clockwise, counter clockwise, or clockwise and counterclockwise in the SONET).

Each SONET link 18 may comprise one or more physical data transmissionlinks. For example, each SONET link 18 may comprise a single physicaltransmission medium (e.g., optical transmission medium such as fiberoptic cabling) coupled to a first SONET framer device at a first nodeand a second SONET framer device at a second node. Alternatively, eachSONET link 18 may comprise a plurality of aggregated physicaltransmission media where each physical transmission medium is coupled toone of a plurality of SONET framer devices at a first node and one of aplurality of SONET framer devices at a second node.

The SONET links 18 coupling nodes 12 in a first SONET ring 14 may becapable of transmitting data between nodes 12 in SONET frames at a firstset data rate. The SONET links coupling nodes 12 in a second SONET ring16 may be capable of transmitting data between nodes 12 in SONET framesat a second set data rate higher than the first set data rate. Forexample, SONET links 18 in the first SONET ring 14 may be capable oftransmitting data at about 625 Mbps in an OC-12 format, for example,while SONET links in the second SONET ring 16 may be capable oftransmitting data at about 2.5 Gbps in an OC-48 format. However, theseare merely examples of different data transmission rates and formatsthat may be employed in SONET links and embodiments of the presentinvention are not limited in these respects.

According to an embodiment, one or more SONET links 18 coupled betweennodes 12 may be provisioned into one or more SONET circuits using anyone of several techniques including, for example, ContiguousConcatenation, Channelized Circuit creation or Virtual Concatenationwhere a portion of the data transmission capacity in each SONET link maybe allocated to a SONET circuit provisioned between nodes 12. However,these are merely examples of techniques that may be used to provision aSONET circuit and embodiments of the present invention are not limitedin these respects. In one example, the payload portion of SONET framestransmitted in a SONET link 18 may be partitioned into “time slots”which are allocated among SONET circuits sharing the transmissioncapacity of the SONET link 18. According to an embodiment, a SONET link18 coupled between nodes 12 may be partitioned among multiple SONETcircuits where each SONET circuit is allocated one or more time slots inSONET link 18. For example, the payload portion of SONET framestransmitted a SONET link capable of transmitting data between nodes 12at an OC-48 transmission rate may be portioned into four time slots,each time slot being allocated to an OC-12 SONET circuit. However, thisis merely an example of how SONET frames transmitted in a SONET link maybe allocated among SONET circuits and embodiments of the presentinvention are not limited in these respects.

According to an embodiment, a SONET circuit may be provisioned from asource node to a destination node that are not coupled together by acommon SONET link. For example, a SONET circuit may be provisionedbetween node 12 _(a) and 12 _(c) where either node 12 _(d) or 12 _(b) isa “participating” intermediate node. If, for example, node 12 _(b) is aparticipating intermediate node, one or more time slots in the SONETlink 18 coupled between nodes 12 _(a) and 12 _(b), and in the SONET link18 between nodes 12 _(b) and 12 _(c), may be allocated to the SONETcircuit (leaving node 12 _(d) as a non-participating node).

According to an embodiment, the data transmission capacity of each SONETlink 18 may be partitioned into a plurality of time slots that may beallocated to a SONET circuit. Each time slot may be associated with atime slot status such as, for example, “provisioned” or “free.” A timeslot may have a provisioned status if currently allocated to a SONETcircuit. A time slot may have a free status if it is not currentlyallocated to a SONET circuit and is available to be allocated to a SONETcircuit. However, these are merely examples of a status that may beassociated with a time slot and embodiments of the present invention arenot limited in these respects.

In an alternative embodiment, a SONET circuit may be provisioned betweennodes in different SONET rings. For example, a SONET circuit may beprovisioned between node 12 _(a) (on SONET ring 14) and node 12 _(g) (onSONET ring 16). In this example, node 12 _(b) common to both SONET rings14 and 16, is an intermediate participating node while nodes 12 _(d), 12_(c), 12 _(e) and 12 _(f) are non-participating nodes.

According to an embodiment, a first node 12 may be capable of initiatinga provisioning of a SONET circuit between itself and a second node 12.The first node 12 may initiate an allocation of one or more time slotsin one or more SONET links coupled between the first node 12 and thesecond node 12 where each of the allocated time slots is to be used inthe provisioned SONET circuit. One or more of the nodes 12 (includingthe first node 12) may maintain a database associating each time slot inthe one or more SONET links with its time slot status. For example, thefirst node 12 may maintain a database associating a time slot statuswith each of the time slots in each SONET link coupled between the firstand second nodes. Based upon information in the database, the first node12 may initiate an allocation of time slots from among the free timeslots to initiate provisioning of the SONET circuit. Upon provisioningof the SONET circuit by an allocation of free time slots, the status ofthe allocated time slots may be changed from free to provisioned.

FIG. 2 shows a topology of a SONET ring in a SONET network according toan embodiment of the topology shown in FIG. 1. Nodes 102 are coupled bySONET links 118 to transmit SONET frames. In addition to the SONET links118, the nodes 102 are coupled to one another by control links 108 to beused in transmitting status information associated with time slots inthe SONET links 118. According to an embodiment, a node 102 may initiateallocation of time slots in SONET links coupled to one or moreparticipating nodes 102 using SONET control protocols such as protocolsprovided in the User Network Interface 1.0 Signaling Specification, Oct.1, 2001, published by the Optical Internetworking Forum(hereinafter-“the UNI Specification”). However, these are merelyexamples of protocols that may be used to allocate data transmissionresources in SONET links coupled between nodes and embodiments of thepresent invention are not limited in these respects.

In one example, node 102 _(a) may initiate provisioning a SONET circuitbetween nodes 102 _(a) and 102 _(b) by allocating one or more “free”time slots (as indicated in the database associated with node 102 _(a))in the SONET link 118 _(a). The SONET link 118 _(a) may have a datatransmission capacity of OC-12 that may be partitioned into twelve timeslots. Protocols according to the UNI Specification may be used toprovision a SONET circuit 106 having a transmission capacity of OC-3 byallocating three of the twelve time slots to the SONET circuit 106.

Upon allocation of the one or more time slots, the node 102 _(a) maytransmit a time slot status message on a control link 108 _(a) toindicate that the status of the allocated time slots has changed fromfree to provisioned. Upon receipt of the time slot allocation message,the node 102 _(d) may forward the time slot status message to node 102_(c), on control link 108 _(b). This forwarding of the time slot statusmessage may continue until it has been received at all of thenon-participating nodes 102 (e.g., ending at node 102 _(c) in thepresently illustrated embodiment). Upon receipt of the time slot statusmessage, each non-participating node 102 may update its databaseassociating a time slot status with the allocated time slots to indicatethat the allocated time slots are provisioned.

In addition to initiating an allocation of one or more time slots toprovision a SONET circuit, a node 102 may initiate a de-allocation ofthe allocated time slots to de-provision or “tear down” the SONETcircuit (e.g., using protocols provided in the UNI Specification). Forexample, node 102 _(a) may transmit a message to 102 _(b) tode-provision the SONET circuit 106 by releasing time slots allocated.Upon release of the allocated time slots, the node 102 _(a) may alsotransmit a time slot status message to the non-participating nodes 102_(d) and 102 _(c) on control links 108 _(a) and 108 _(b) to indicate achange in status of the released time slots. Upon receipt of the timeslot status message, the non-participating nodes 102 _(d) and 102 _(c)may each update its database associating a time slot status with thede-allocated time slots to indicate that the de-allocated time slots arefree.

FIG. 3 shows a schematic diagram of a system at a first node to transmitdata to a second node according to an embodiment of the SONET networkshown in FIG. 2. A framer/mapper 214 may comprise a SONET framer toreceive and transmit SONET frames and a mapper to map services to datapaths in the SONET frames. The framer/mapper 214 may be coupled to atransceiver/transponder 216 to transmit or receive data in an opticaltransmission medium. The framer/mapper 214 may provide one or more SONETpaths to transmit data to or receive data from a switch/router 202 overa standard data interconnection such as versions of a System PacketInterface (e.g., SPI-4, SPI-4 phase II or SPI 5) or UTOPIA bus, or aproprietary data interconnection. A circuit controller 212 may compriselogic to provision or de-provision one or more SONET circuits defined inthe framer/mapper 214.

The framer/mapper 214 may transmit SONET frames to or receive SONETframes from another node in a SONET ring (e.g., a node 102 as shown inFIG. 2). The framer/mapper 214 may also associate portions of a payloadin SONET frames transmitted to or received from a SONET link with timeslots that may be allocated to one or more SONET circuits. According toan embodiment, the framer/mapper 214 may be dynamically configured toassociate time slots with SONET circuits in response to commands fromthe circuit controller 212. In response to a provisioning of a SONETcircuit, for example, the circuit controller 212 may configure theframer/mapper 214 to associate the provisioned SONET circuit with one ormore allocated time slots of a SONET link.

The circuit controller 212 may comprise logic to transmit messages to orreceive messages from a circuit controller at another node (not shown)to provision and de-provision SONET circuits in one or more SONET links.For example, the circuit controller 212 may comprise logic to provisionand de-provision SONET circuits using protocols such as those providedin the UNI Specification. Additionally, the circuit controller 212 maycomprise logic to transmit time slot status messages to, or receive timeslot messages from, non-participating nodes in a control link (e.g.,control link 108). While acting as part of non-participating node, thecircuit controller 212 may also comprise logic to receive time slotstatus messages from a control link and update a database associatingtime slots in a SONET link with a time slot status.

Logic in the circuit controller 212 may comprise a processor to executemachine-readable instructions stored in a storage medium. Alternatively,logic in the circuit controller 212 may comprise an ASIC or FPGA. In oneembodiment, a control link to transmit messages between the circuitcontrollers of respective nodes may comprise an in-band messaging linkencapsulated in SONET frames. Alternatively, the control link maycomprise an out of band medium such as an Ethernet data link. However,these are merely examples of how circuit controllers of different nodesin a SONET ring may transmit and receive time slot status messages andembodiments of the present invention are not limited in these respects.

FIG. 4 shows a flow diagram illustrating a process 300 executed at anode in response to provisioning a SONET circuit according to anembodiment of the system shown in FIG. 3. At block 302, one or more timeslots in SONET links coupled to participating nodes are selected for usein provisioning a SONET circuit. The selected time slot(s) may beselected from among time slots in a SONET link that are associated witha “free” status indication in a database. A circuit controllerassociated with the node initiating the creation of the SONET circuitmay then update the database to indicate a change in status of the timeslot from free to provisioned. To complete the allocation of theselected time slot(s) to the SONET circuit, at block 304, messages maybe transmitted to or received from participating nodes according toprotocols provided in the UNI Specification. Upon completion ofallocating the selected time slot(s), block 306 may initiatetransmission of time slot status messages to non-participating nodes toindicate a change in status of the allocated time slots.

FIG. 5 shows a flow diagram illustrating a process 350 executed at anode to de-allocate time slots in response to a de-provisioning of aSONET circuit according to an embodiment of the system shown in FIG. 3.At block 352, a circuit controller may detect an event (e.g., a “teardown” event) to de-provision a SONET circuit and update a databaseassociated with the node to change the status of affected time slotsfrom provisioned to free. At block 354, the circuit controller maycommunicate with participating nodes to de-allocate time slots allocatedto the SONET circuit. For example, the circuit controller may transmitmessages to or receive messages from the participating nodes accordingto protocols provided in the UNI Specification. Block 356 may theninitiate transmission of time slot status messages to non-participatingnodes to indicate a change in status of the de-allocated time slots fromprovisioned to free.

FIG. 6 shows a format for a packetized time slot status message 400 tobe transmitted to non-participating nodes in a control link according toan embodiment of the processes shown in FIGS. 4 and 5. The formatcomprises a plurality of fields including a Ring ID field 402, Time Slotfield 404, a Status Field 406 and one or more Node fields 410. The RingID field 402 may uniquely identify a SONET ring and Node fields 410 mayuniquely identify participating nodes in the SONET ring that are used ina SONET circuit. Accordingly, non-participating nodes in the associatedSONET ring to receive the message 400 may not be listed in Node fields410. If non-participating nodes on other SONET rings in a SONET networkare to receive the time slot status message 400, an additional time slotstatus message may be formulated for each additional SONET ring.

The Time Slot field 404 may uniquely identify a time slot of a SONETlink that may be allocated for provisioning a SONET circuit. The TimeSlot field 404 may comprise information associated with a SONET “Line”coupled between nodes and a portion of SONET frames transmitted in theSONET line between line terminating equipment (LTE) at each node.However, this is merely an example of how a time slot in a SONET linkmay be identified and embodiments of the present invention are notlimited in these respects. The Status field 406 may indicate the statusof the time slot identified in the Time Slot field 404 as either free orprovisioned as described above.

According to an embodiment, the Node field 410 ₁ may identify a sourcenode at a first endpoint of a SONET circuit that initially transmits thetime slot status message 400, and a Node field 410 _(n) may identify adestination node at a second endpoint of the SONET circuit. Node fields410 ₂ through 410 _(n−1) may then identify intermediate nodes in theSONET circuit between the source node and the destination node. Thesource node may transmit the time slot status message 400 to anon-participating node that is not identified in the Node fields 410.Upon receipt of the time slot status message, a circuit controller at anon-participating node may update a database to reflect a change in astatus (as indicated in Status field 406) of a time slot identified inTime Slot field 404. The circuit controller may then transmit the timeslot status message 400 to a subsequent non-participating node in theSONET ring. The time slot status message 400 may be repeatedly forwardedto non-participating nodes in the SONET ring until received by eachnon-participating node. Upon receipt of the time slot status message400, a participating node (e.g., either the source node identified inNode field 410 ₁ or the destination node identified in Node field 410_(n)) may terminate forwarding the time slot status message 400 to anyother node.

The time slot allocation message 400 may be transmitted to a circuitcontroller (e.g., at block 306 or 356) using any one of several in-bandor out-of-band messaging techniques. In one in-band messaging technique,for example, the time slot status message 400 may be encapsulated in aportion of a Data Communication Channel (DCC) of a SONET Section or LineOverhead of a SONET frame (e.g., transmitted in a SONET link coupledbetween node in a SONET ring). A portion of the time slot allocation 400may be transmitted in the header of each of a sequence of SONET framestransmitted to a recipient node. Within a SONET Section Overhead, forexample, the time slot allocation message 400 may be encapsulated inuser defined bytes D1-D3. Alternatively, the time slot allocationmessage 400 may be encapsulated in SONET Line Overhead bytes D4-D12.Within the DCC, the time slot status message 400 may also beencapsulated in a data link frame according to a link-level protocolsuch as the High-level Data Link Control (HDLC) protocol. Upon receiptof the encapsulated data link frame, the encapsulated control link framemay be processed for message detection and verification to receive thetime slot status message 400. A circuit controller at a receiving nodemay then use the information in the time slot status message 400 toupdate the status of the time identified in Time Slot field 404.

In an alternative to encapsulating the time slot status message 400 in aDCC, the time slot status message 400 may be encapsulated in an out ofband message. For example, the link aggregation message may betransmitted between a data link controller at transmitting node to acircuit controller at a receiving node in an out-of-band messageaccording to a Link Management Protocol or RSVP-TE protocol. Forexample, the circuit controller at transmitting node to a circuitcontroller at a receiving node may be coupled to an Ethernet connectionto transmit the link aggregation. However, this is merely an example ofhow a link aggregation message may be transmitted between circuitcontrollers in an out-of-band message and embodiments of the presentinvention are not limited in these respects.

FIG. 7 shows a flow diagram illustrating a process 500 executed at anode upon receipt of a time slot status message at a node according toan embodiment of the packetized time slot status message shown in FIG.6. At block 502, a circuit controller at the node may receive the timeslot status message on an in-band or out-of-band control link. If therecipient node is the last node to receive the time slot status messageas determined at diamond 504, the time slot status message may not beforwarded. According to the embodiment of the time slot status message400 shown in FIG. 6, a participating node such as the destination nodeidentified in the last Node field 410 _(n) receiving the time slotstatus message may determined that it is the last node by detecting itsidentifier in a Node field 410. Otherwise, if the recipient node is notthe last node to receive the time slot status message, the circuitcontroller may update a local database to indicate a change in thestatus of the time slot identified in the time slot status message atblock 506, and may forward the time slot status message to another nodeat block 508.

The embodiment of FIG. 7, if the recipient node is the last node toreceive the time slot status message, a circuit controller associatedwith the recipient node suspends forwarding the time slot status messageand does not update a local database to indicate a change in statusassociated with a time slot. In other embodiments, however, the lastrecipient node may update a local database (e.g., if the last recipientnode is a non-participating node). For example, the last recipient nodemay be a non-participating node that updates a local database toindicate a change in status associated with a time slot and ceasesforwarding the time slot status message 400 if the next node that is toreceive the message 400 is the destination node identified in field 410_(n).

In the embodiment shown in FIG. 2, the node 102 _(a) may initiate aprovisioning of a SONET circuit to node 102 _(b) in a “clockwise”direction in the SONET ring topology by initiating an allocation of timeslots in link 118 _(a). Correspondingly, the node 102 _(a) may initiateforwarding of time slot status messages to non-participating nodes 102in a “counter clockwise” direction in the SONET ring topology accordingto the embodiments illustrated in FIGS. 4 through 6. Non-participatingnodes 102 may then forward time slot status messages in the counterclockwise direction according to the embodiment of process 500 shown inFIG. 7.

For example, the time slot status message 400 may list all participatingnodes in the SONET ring in order from the source node to the destinationnode in the clockwise direction in Node fields 410 ₁ through 410 _(n). Acircuit controller at each node in the SONET ring receiving the message400 may determine whether the node is the last node to receive themessage 400, at diamond 504, by determining whether the recipient nodeis the destination node identified in Node field 410 _(n). If therecipient node is the destination node, for example, diamond 504 maydetermine that the message 400 is not to be forwarded to another node.

By forwarding time slot status messages in a direction opposite to thedirection of the SONET circuit, the time slot status message need nottraverse the participating nodes 102 which may add delay. Accordingly,the recipient non-participating nodes 102 may update local databases toreflect changes in the status of time slots more quickly than if timeslot status messages were forwarded in the same direction of the SONETcircuit.

While there has been illustrated and described what are presentlyconsidered to be example embodiments of the present invention, it willbe understood by those skilled in the art that various othermodifications may be made, and equivalents may be substituted, withoutdeparting from the true scope of the invention. Additionally, manymodifications may be made to adapt a particular situation to theteachings of the present invention without departing from the centralinventive concept described herein. Therefore, it is intended that thepresent invention not be limited to the particular embodimentsdisclosed, but that the invention include all embodiments falling withinthe scope of the appended claims.

1. A system comprising: a switch fabric comprising a plurality of ports;a plurality of SONET framers, each SONET framer being coupled to a portof the switch fabric; and a circuit controller at a source node totransmit data to a destination node in a SONET network, and coupled toat least one of the SONET framers, the circuit controller comprising:logic to initiate an allocation of one or more time slots in SONET linkscoupled between the source node and the destination node to provision aSONET circuit between the source and destination nodes, wherein a datatransmission capacity of each said SONET link corresponds to the numberof said time slots allocated to said each SONET link, each of said timeslots being allocated to a distinct service or process; and logic toinitiate transmission of a time slot status message to one or more nodesin the SONET network which are not in the provisioned SONET circuit, thetime slot status message identifying at least one allocated time slotwithin said provisioned SONET circuit, said time slot status messageincluding a Ring ID field, a time slot field, a status field and atleast one node field.
 2. The system of claim 1, wherein each SONETframer is coupled to a port of the switch fabric by an interconnectionformed according to a System Packet Interface.
 3. A method executable ata source node to transmit data to a destination node in a SONET network,comprising: initiating an allocation of one or more time slots in SONETlinks coupled between the source node and the destination node toprovision a SONET circuit between the source and destination nodes,wherein a data transmission capacity of each said SONET link correspondsto the number of said time slots allocated to each said SONET link, eachof said time slots being allocated to a distinct service or process; andinitiating transmission of a time slot status message to one or morenodes in the SONET network which are not in the provisioned SONETcircuit, the time slot status message identifying at least one allocatedtime slot within said provisioned SONET circuit, said time slot statusmessage including a Ring ID field, a time slot field, a status field andat least one node field.
 4. The method of claim 3, wherein the time slotstatus message comprises information identifying one or more nodes inthe SONET network that are to receive the time slot status message. 5.The method of claim 3, the method further comprising: initiating anallocation of a plurality of time slots in the one or more SONET links;and initiating transmission of a time slot status message to the one ormore nodes in the SONET network which are not in the provisioned SONETcircuit for each of the allocated time slots.
 6. The method of claim 3,the method further comprising initiating the allocation of the one ormore time slots based upon protocols defined in a User NetworkInterface.
 7. The method of claim 3, the method further comprising:initiating a de-allocation of one or more time slots in at least oneSONET link coupled between the source node and the destination node tode-provision the SONET circuit; and initiating transmission of a secondtime slot status message to the one or more nodes not in the provisionedSONET circuit, the time slot status message identifying at least onede-allocated time slot.
 8. A controller at a source node to transmitdata to a destination node in a SONET network, comprising: logic toinitiate an allocation of one or more time slots in SONET links coupledbetween the source node and the destination node to provision a SONETcircuit between the source and destination nodes, wherein a datatransmission capacity of each said SONET link corresponds to the numberof said time slots allocated to each said SONET link, each of said timeslots being allocated to a distinct service or process; and logic toinitiate transmission of a time slot status message to one or more nodesin the SONET network which are not in the provisioned SONET circuit, thetime slot status message identifying at least one allocated time slotwithin said provisioned SONET circuit, said time slot status messageincluding a Ring ID field, a time slot field, a status field and atleast one node field.
 9. The controller of claim 8, wherein the timeslot status message comprises information identifying one or more nodesin the SONET network that are to receive the time slot status message.10. The controller of claim 8, the controller further comprising: logicto initiate an allocation of a plurality of time slots in the one ormore SONET links; and logic to initiate transmission of a time slotstatus message to the one or more nodes in the SONET network which arenot in the provisioned SONET circuit for each of the allocated timeslots.
 11. The controller of claim 8, the controller further comprisinglogic to initiate the allocation of the one or more time slots basedupon protocols defined in a User Network Interface.
 12. The controllerof claim 8, the controller further comprising: logic to initiate ade-allocation of one or more time slots in at least one SONET linkcoupled between the source node and the destination node to de-provisionthe SONET circuit; and logic to initiate transmission of a second timeslot status message to the one or more nodes not in the provisionedSONET circuit, the time slot status message identifying at least onede-allocated time slot.
 13. An article at a source node to transmit datato a destination node in a SONET network, the article comprising astorage medium having stored thereon instructions that when executed bya machine result in the following: initiate an allocation of one or moretime slots in SONET links coupled between the source node and thedestination node to provision a SONET circuit between the source anddestination nodes, wherein a data transmission capacity of each saidSONET link corresponds to the number of said time slots allocated toeach said SONET link, each of said time slots being allocated to adistinct service or process; and initiate transmission of a time slotstatus message to one or more nodes in the SONET network which are notin the provisioned SONET circuit, the time slot status messageidentifying at least one allocated time slot within said provisionedSONET circuit, said time slot status message including a Ring ID field,a time slot field, a status field and at least one node field.
 14. Thearticle of claim 13, wherein the time slot status message comprisesinformation identifying one or more nodes in the SONET network that areto receive the time slot status message.
 15. The article of claim 13,wherein the storage medium further comprises machine-readableinstructions stored thereon to: initiate an allocation of a plurality oftime slots in the one or more SONET links; and initiate transmission ofa time slot status message to the one or more nodes in the SONET networkwhich are not in the provisioned SONET circuit for each of the allocatedtime slots.
 16. The article of claim 13, wherein the storage mediumfurther comprises machine-readable instructions stored thereon toinitiate the allocation of the one or more time slots based uponprotocols defined in a User Network Interface.
 17. The article of claim13, wherein the storage medium further comprises machine-readableinstructions stored thereon to: initiate a de-allocation of one or moretime slots in at least one SONET link coupled between the source nodeand the destination node to de-provision the SONET circuit; and initiatetransmission of a second time slot status message to the one or morenodes not in the provisioned SONET circuit, the time slot status messageidentifying at least one de-allocated time slot.
 18. A method executableat a first node to transmit data to a second node in a SONET networkcomprising: receiving a first time slot status message at said firstnode in a SONET ring which is not in a provisioned SONET circuit, thefirst time slot status message identifying a status of at least one timeslot in a SONET link coupled between at least two nodes in saidprovisioned SONET circuit, wherein a data transmission capacity of saidSONET link corresponds to the number of said time slots allocated toeach said SONET link, each of said time slots being allocated to adistinct service or process; updating a status associated with the timeslot in a database associated with said first node in response to thefirst time slot status message; and forwarding a second time slot statusmessage from said first node to a second node in the SONET ring which isnot in said provisioned SONET circuit, the second time slot statusmessage being based, at least in part, upon the first time slot statusmessage, said first and second time slot status messages including aRing ID field, a time slot field, a status field and at least one nodefield.
 19. The method of claim 18, wherein the first time slot statusmessage comprises information identifying one or more nodes in the SONETcircuit that are to receive the first time slot status message.
 20. Themethod of claim 18, wherein receiving the first time slot status messagecomprises receiving the first time slot status message in a data frameencapsulated in a header portion of one or more SONET frames.
 21. Themethod of claim 20, wherein forwarding the second time slot statusmessage comprises forwarding the second time slot status message in adata frame encapsulated in a header portion of one or more SONET frames.22. The method of claim 18, wherein receiving the first time slot statusmessage comprises receiving the first time slot status message in a dataframe from an Ethernet data link.
 23. The method of claim 22, whereinforwarding the second time slot status message comprises forwarding thesecond time slot status message in a data frame to an Ethernet datalink.
 24. The method of claim 22, the method further comprisingreceiving the first time slot status according to a Link ManagementProtocol.
 25. The method of claim 22, the method further comprisingreceiving the first time slot status message according to an RSVP-TEprotocol.
 26. A controller at a first node to transmit data to a secondnode in a SONET network comprising: logic to receive a first time slotstatus message at said first node in a SONET ring which is not in aprovisioned SONET circuit, the first time slot status messageidentifying a status of at least one time slot in a SONET link coupledbetween at least two nodes in said provisioned SONET circuit, wherein adata transmission capacity of said SONET link corresponds to the numberof said time slots allocated to each said SONET link, each of said timeslots being allocated to a distinct service or process; logic to updatea status associated with the time slot in a database associated withsaid first node in response to the first time slot status message; andlogic to forward a second time slot status message from said first nodeto a second node in the SONET ring which is not in said provisionedSONET circuit, the second time slot status message being based, at leastin part, upon the first time slot status message, said first and secondtime slot status messages including a Ring ID field, a time slot field,a status field and at least one node field.
 27. The controller of claim26, wherein the first time slot status message comprises informationidentifying one or more nodes in the SONET circuit that are to receivethe first time slot status message.
 28. The controller of claim 26, thecontroller further comprising logic to receive the first time slotstatus message comprises in a data frame encapsulated in a headerportion of one or more SONET frames.
 29. The controller of claim 28, thecontroller further comprising logic to forward the second time slotstatus message in a data frame encapsulated in a header portion of oneor more SONET frames.
 30. The controller of claim 26, the controllerfurther comprising logic to receive the first time slot status messagein a data frame from an Ethernet data link.
 31. The controller of claim30, the controller further comprising logic to forward the second timeslot status message in a data frame to an Ethernet data link.
 32. Thecontroller of claim 30, the controller further comprising logic toreceive the first time slot status according to a Link ManagementProtocol.
 33. The controller of claim 30, the controller furthercomprising logic to receive the first time slot status message accordingto an RSVP-TE protocol.